The intradermal Leishmanin reaction induces antigen-specific maturation of canine dendritic cells with up-regulation of MHCII synthesis and expression.

Dendritic cells (DCs) are professional antigen-presenting cells that reside in many tissues, including the skin. This study showed that intradermal injection of leishmanin in Leishmania infantum-infected dogs induced the "up-regulation" of surface MHCII expression, associated with progressive ultrastrucutural changes characteristic of DC maturation, including the formation of multilaminar MHC class II-containing compartments and arrays of tubulo-vesicular structures. These changes were not observed in control dogs from L. infantum non-endemic areas. The results indicated that canine DCs were effector cells in delayed-type hypersensitivity, that the leishmanin reaction was specific for a cell-mediated reaction to L. infantum in infected dogs, and that canine DCs possessed ultrastructural organelles reminiscent of those in activated human DCs.